Another surprise was the announcement that finasteride reduces the risk of prostate cancer by 25% with no change in the risk for high-grade tumors. Initial reports from the Prostate Cancer Prevention Trial indicated that while finasteride reduced prostate cancer by 25%, it also produced a 25% increase in high-grade tumors. Later analysis showed that the jump in high-grade tumors was linked to finasteride's ability to shrink an enlarged prostate by 25%.
"If you do the same number of biopsies in a smaller gland as in an enlarged gland, it stands to reason that you will find more cancers," explained Eric Klein, M.D., professor of surgery at the Cleveland Clinic Lerner College of Medicine of Case Western Reserve University. "The data support that conclusion."
Finasteride also increases the diagnostic accuracy of PSA testing. Putting a patient on finasteride should reduce PSA by about 50%, Klein said. If there is no PSA drop after initiating finasteride, or if PSA shows any increase during treatment, the prostate should be biopsied immediately. Using finasteride to prevent prostate cancer is off-label, Klein cautioned.
The evidence on overactive bladder (OAB) is less conclusive. "I don't think there is any one drug that will work for everyone," said David Staskin, M.D., director, female urology and urodynamics, at New York Presbyterian-Cornell Hospital. "OAB is a collection of symptoms," he continued. "There are differences in drugs between targets, effects, and side effects. If one doesn't work, try titrating the dose or try another agent."
Five antimuscarinic agents are approved for overactive bladder, said Victor Nitti, M.D., associate professor and vice chair of urology at the New York University School of Medicine:
These antimuscarinic agents are not identical or interchangeable, Nitti added.